Appeal

"Say the phrase, stranger, if you like your neck unburdened with the rope."
~Iliac, culture hero
When Cerin Gorbil first recruited Iliac and his gang of miscreants, one of the lessons he taught them was to strike with the weight of ancestors behind them. With mindfulness of the ancient warriors stretching out behind you, your courage never falters for fear of shaming them. Of the many phrases he taught the young warriors was, "ka nama ka lajerama," translated as 'Breathe oh sleeping dead! Thy breath is the death of the enemies of the gods!'
When Iliac's friend, Sombren, could not speak the phrase, that is when it was learned that the shape of yuan-ti mouths were simply incapable of uttering the syllables properly. Sombren turned out to be a spy, and the phrase became Iliac's battlecry as well as the standard watchphrase, and yuan-ti infiltrators were never again a threat to the camp.
It is sometimes used as a slur, shortened to Kanama. The slur either refers to Scalykind, or someone sufficiently cold blooded to resemble them.